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BJ 722p! Reader l +Rfren g Pater/fia- I 1 Meter United States Patent3,445,071 METHOD AND APPARATUS FOR WINDING A PRECISION RESISTOR CharlesF. Kezer, Mineola, and Thomas P. Zingarelh II, New York, N.Y., assignorsto Litton Industries, Inc., Beverly Hills, Calif., a corporation ofDelaware Filed June 14, 1967, Ser. No. 646,019

Int. Cl. B65h 81/06; G01v; Gf US. Cl. 242-7.03 12 Claims ABSTRACT OF THEDISCLOSURE A method and apparatus for controlling a winding machine formaking the resistor element of a potentiometer. The apparatus employs aprogramming arrangement having signal-sensing and -storage means forcontrol signals. In the illustrative embodiment, the stored digitalsignals encoded on tape are converted into analog signals which areutilized to control the spacing of the turns of resistance wire whichforms the resistor being wound on the winding machine, in order toobtain a desired spatialresistance characteristic. Changes in thefunctional characteristics of the wound resistor are effected by using adifferent input element (tape). The apparatus also includes checkingmeans to enable correction of any malfunction of the control system.

This invention relates to methods and apparatus for programming thewinding operation of a machine for winding the precision resistorelement of a potentiometer, and for guarding against improper operationof the control apparatus.

It is an object of the invention to improve the programming of aprecision winding machine that may be used for winding the resistorelement of a potentiometer, to Simplify the time-consuming method ofprogramming the winding machine as practiced heretofore, and toeliminate human error in the operation of the machine.

A more specific object of the invention is the provision, in theprogramming arrangement for a winding machine of this character, ofsignal-sensing and -storage means, such as a punched tape and tapereader, for controlling the programming of the machine. In this mannerthe programming may be changed readily to alter the functionalcharacteristics of the resistor being wound by merely substitutingcontrol tapes in the programming unit. Hitherto the programming requiredmanually shifting and wiring a large number of tap connections on amaster or reference standard potentiometer.

Still another object of the invention is to provide a simple andeffective arrangement for detecting malfunctioning of the programmedcontrol system of a winding machine.

For a clearer understanding of the invention, and other objects andadvantages thereof, reference may be made to the illustrativeembodiments of the invention shown in the accompanying drawings, whereinFIG. 1 is a plan view of a typical resistor winding machine in generaluse which is adapted to be controlled by a programming arrangementaccording to the invention;

FIG. 2 is a schematic diagram of the program console embodying theinvention for controlling the servo drive mechanism of the windingmachine;

FIG. 3 is a view, partially schematic, showing the interconnectionsbetween the control section of the program unit and the reference orcontrol potentiometer;

FIG. 4 is a similar view showing the interconnection of the referencepotentiometer, the winding machine and a servomotor input circuit;

FIG. 5 is a view similar to FIG. 4 showing a modification;

FIG. 6 is a diagrammatic view of a system for checking the program unitfor malfunctioning condition; and

FIG. 7 is a view similar to FIG. 3 of a modification in which thecontrol potentiometer is provided with only two taps.

Referring to the drawings, FIG. 1 shows a precision winding machine usedin practice and similar to that shown and described in the .patent to J.R. Altieri, No. 3,203,633, and assigned to the assignee of the presentinvention. The disclosure of said patent is incorporated herein byreference. The winding machine shown in the drawing merely illustratesby way of example a wellknown winding machine to which the controlsystem of the invention may be applied and the invention is not limitedto this particular type of Winding machine.

As shown, the winding machine employs a travelling carriage 10 whichincludes a horizontal base plate 11 on which are supported a spool ofresistance wire 12 and suitable wire-guiding means in cooperativerelation to an insulating mandrel 15 on which the resistance wire iswound to form a precision resistor for a potentiometer. Other parts ofthe machine, including the controlled motor drive, are also well-knownand are illustrated in detail in the prior patent to A. S. J. Lee, No.2,989,256, the disclosure of which is incorporated herein by reference.The carriage 10 is supported for transverse movement on two parallelguide rails 16 and 17, the carriage being fed along the axis of themandrel 15 by a lead screw 18 connected to the servomotor drive 19 whichmay be similar to that described in the Lee patent. The mandrel 15 isrestrained against longitudinal movement and rotated at constant speed.Since the rate of feed of the carriage 10 is proportional to the rate ofrotation of the lead screw 18, the spacing of the resistance wire woundon the mandrel 15 is dependent on the relation between the rotativespeeds of 18 and 15. Thus the servomotor drive for the winding machinecontrols the spacing between the turns of wire on the mandrel 15 inaccordance with the desired functional characteristics of the resistorbeing wound, the variation being controlled by a programmed controlsystem including a control potentiometer as will be described. Duringthe winding operation, the resistance wire 21 is unwound from the spool12 and passes over guide pulleys 22, 23 and 24, and over the guide bar25 to engage the tip end of the nose piece 26 through which the mandrel15 is fed. The nose piece 26 is part of a hollow mandrel guide 27embracing the rotating mandrel 15 and serving to accurately position thepoint of lay of the wire as it is fed onto the winding form or mandrel15, as described in detail in the abovementioned patents. The nose piece26 also provides electrical contact with the wire 21 so that theresistance Rx of the wound portion of the resistor may be continuouslychecked as the winding operation proceeds.

The wire spool 12 is preferably to a rotatable spool shaft 30 connectedto a brake motor 31 to maintain a predetermined tension in theresistance wire being wound on the mandrel 15. A brush 32 is provided incontact with the shaft 30 to supply current to the wire 21 during thewinding operation. A connection may be made to the nose piece 26 andterminal 33 whereby the potential drop across the varying resistance Rxmay be compared with the control potential derived from the control orreference potentiometer during the winding operation to control theservomotor drive for obtaining the desired functional characteristics inthe finished product.

The servomotor drive 19 may consist of low-speed and high-speedservomotors controlled by the connection to the reference potentiometerto maintain a balance between the adjustment of said potentiometer andthe potential drop across the resistance Rx similar to the controldescribed in the above-mentioned Lee patent. However, in prior controlsas exemplified by said patent, the programming arrangement includes amaster reference potentiometer containing a great many tap connectionswhich must be precisely located and shifted in position when the windingmachine is to be operated to produce resistors having differentelectrical characteristics. For example, in practice a 40-turn, 80-tappotentiometer has been commonly used. Making the tap connections is alaborious and time-consuming operation subject to human error, resultingin reject or defective units.

In accordance with the present invention, the programmed control systemconsists of signal-sensing and -storage means for a multiplicity ofcontrol signals, such as a .punched tape and a tape reader, and meansfor successively applying corresponding control voltages to spacedpoints or taps on a linear reference potentiometer with fixed taps. FIG.2 illustrates essentially the novel control system. Referring to thisfigure, the program console comprises a programmed input unit 35including a punched tape and a tape reader 36 connected throughconductors 37 to a register and control section 38. The input unit 35constitutes a control signal-sensing and -storage means. The controlsection 38 is provided with a connection 39 for stepping the tape reader36 to read out successive blocks of stored control signals. The tapereader 36 may, for example, be designed for standard eight-channelpunched tape containing stored signals representing commands, data andinstructions for self-system checkout. A suitable tape reader mechanismis the model 2500 made by Digitronics Corporation of Albertson, LongIsland, N.Y. Theprogramming is achieved by a block format and in atypical system each block consists of digitized signals representing atleast one predetermined voltage or potential followed by the end ofblock command. Once started the tape reader reads at maximum speed,programming the tap voltages as required.

It will be understood that the conventional control systern for aservo-controlled winding machine of this type includes means forcontinuously measuring the resistance of the wound portion of theresistor being formed on the winding machine and a master referencepotentiometer having fixed potential taps and a movable contact orslider which is synchronized with the winding machine; the potentialdrop in the wound portion of the resistor being compared with thereference potential from the master potentiometer, and the differencebetween said potentials being utilized to continuously control theservomotor drive to obtain the desired functional characteristics in thewound element. In order to obtain control potentials to control thewinding operation, in accordance with the present invention, signalstorage means is employed to store control signals which are convertedto voltages or potentials applied in succession at predetermined timesto a reference potentiometer having two or more fixed taps.

In the embodiment shown in FIG. 2 the stored control signals in theregister section 38 having three output channels are converted fromdigital to analog signals in the D/A converters 41, 42 and 43. A source49 of reference voltage is connected to the D/A converters. Obviouslythe control signals may be stored in any suitable manner and, if storedin analog form on a tape or other storage medium, the D/A converterswould not be required. The output potentials of the respectiveconverters are impressed upon the equally spaced taps Nos. 1, 2 and 3 ofthe linear resistance 45 of a reference potentiometer 46, whichcorresponds to the master potentiometer used heretofore. The principaladvantages of this control system are that a simple referencepotentiometer having a few fixed taps replaces the multiturn masterpotentiometer having a multiplicity of taps as used in the prior art,and the functional characteristics of different resistance elementsbeing wound may be varied by substituting different input elements suchas punched tapes instead of modifying the many tap connections to themaster potentiometer whenever the winding machine is to be operated toform a different resistance element. Thus the system is more reliableand much simpler to set up. Furthermore, the length of the resistanceelement to be wound may be changed readily merely by changing the gearratio in the drive connection from the winding machine to the movablecontact member of the master potentiometer.

In order to achieve the required level of system accuracy, flexibilityand speed, a relatively large quantity of numerical data and alphabeticcommands must be stored and utilized by the control console in a shortperiod of time. This requirement is met by the present system involvingthe use of computer-type logic for quick access to control data. Afterthe program input console has been prepared, the operator merely closesa start switch which advances the tape to the initial start point. Theservo drive for the winding machine is then turned on and thedifferential or error voltage between the master potentiometer and theresistance Rx of the wound portion of the resistor then controls theservo drive of the winding machine to change the pitch of the winding asrequired. After the movable contact or slider 47 of potentiometer 46 hasadvanced to a predetermined point, the tape advances to program adifferent potential on one of the taps of potentiometer 46, and thiscycle is repeated until the winding is finished.

The register and control section 38 may be of any well known type,depending upon the character and functioning of the control signalstorage. In the system illustrated employing punched tape by way ofexample, the stored control signals are set up in conventional registerswhich apply corresponding signals through the D/A converters in thethree signal channels to the potentiometer 46 in timed relation to thewinding operation and the consequent advance of the movable contact orslider 47. In practice, a voltage divider is utilized in each channelwhich may be a relay-operated voltage divider such as the model RVD-lOSmanufactured by Julie Research Laboratories, New York, N.Y. By the useof conventional registers and amplifiers, the voltage ratio receivedfrom the tape in serial digit form is converted by means of theregisters to parallel digit form for transmission to the code converters41, 42, 43, and the taps on the potentiometer 46. The amplifiers in eachcontrol signal channel may be Philbrick operational amplifiers, modelUSA-3, made by George A. Philbrick Researches, Inc. of Boston, Mass.Obviously various other code storage, readout and converter arrangementsknown in the art may be employed to apply the desired successive controlvoltages at proper intervals to the taps of the potentiometer 46.

Referring to FIGS. 3 and 4, the three control channels are shown asincluding operational amplifiers, 51, 52 and 53, and relays 54, 55 and56 in the respective channels to connect and disconnect the referencevoltages as the programmed input is stepped and the slider 47 advancesfrom one tap to the next on resistance element 45. The steppingfunctions maybe performed in any suitable manner. As shown, the shaft ofthe slider 47 is connected to an apertured disc 61 having three equallyspaced apertures 62. The disc 61 cooperates with a photoelectric impulsegenerator 63 which may consist of a lamp 64 and a photosensitive pickupelement 65 arranged on opposite sides of the disc 61. As the disc 61rotates, the apertures 62 are brought into registry with the light fromthe lamp 64 to generate control pulses in timed relation to the rotationof the slider 47. These control pulses may then be used in an obviousmanner to control the tape reader 36 to step the tape, as well as toreset the registers in the control section 38 and selectively operaterelays 54, 55 and 56. When slider 47 is in the position shown in FIG. 3,the contacts of relays 54 and 55 connect channels 1 and 2 to taps 1 and2 on resistance 45; subsequent- 1y channels 2 and 3 are connected totaps 2 and 3, and so on, by relays 54-56.

FIG. 4 illustrates the manner in which the potentiometer 46 issubstituted for the master potentiometer in the control system of theprior art, for example as shown in the patents referred to above. Asindicated, the power supply 74 may be employed as a source of referencepotential for the D/A converters 41, 42 and 43. The control for thewinding machine includes a constant-current source 68 and terminals 69of the servomotor drive mechanism which are explained in detail in theAltieri patent and require no further description. The constant-currentsource 68 is a high-gain amplifier with feedback to maintain a constantoutput current irrespective of changes in the resistance of the loadcircuit. A suitable current source of this type is the Model CS-llPrecision Current Source manufactured by North Hills Electronics, Inc.,of Glen Cove, Long Island, NY. The resistance Rx of the wound portion ofthe resistance element is measured by contact brushes 70 and 71 inseries with one of the terminals 69 and the power supply 74. Theservomotor drive responds to the differential voltage between theterminals 69. The elements 72 to 77 may be similar to the correspondingelements of the control system described in the Altieri patent, and thecontrol of the servomotor drive will be obvious to those skilled in theart, even without reference to the prior patents mentioned. The circuitsand apparatus shown in FIGS. 3 and 4, with the exception ofpotentiometer 46 and its input control circuits, are conventional.

Instead of using a constant-current source in series with the resistanceelement being wound, and a signal input arragement for the referencestandard as described above and shown in FIGS. 1 to 4, a linear masterpotentiometer of the usual type may be used with a current source of thesame type as source 68 but having its output current varied to obtaineither linear or nonlinear functional characteristics of the resistorunder the control of the program unit, thus eliminating the requirementfor a multiplicity of taps on the master potentiometer. Thismodification is shown in FIG. 5, which is similar to FIG. 4 except thatthe master potentiometer 80 is a simple linear potentiometer which canbe used for winding either linear or non-linear resistor elements byvariation of the output current from an adjustable constant-currentsource 81, such as the Current Source of North Hills Electronics, Inc.,referred to above. In this modification the tape reader 36 and aregister 38 may be similar to the tape reader and register describedabove or any other suitable means for generating the control inputvoltages. A D/A converter 82 is used to generate a potential varying inamplitude in accordance with the signal input and operative to vary theinput of the operational amplifier 83 in the current source unit andthereby vary the output current of the source 81. The current source 81may also include a power amplifier 84. It will be apparent that thefunctional characteristics of the resistor element being wound may bevaried in a predetermined manner under the control of the program unitin response to variations in the output current of source 81. Thus thesame result is obtained without varying the potentials applied to thetaps of the reference potentiometer.

In order to detect malfunctioning of the programming and control system,the test or checking circuit shown in FIG. 6 may be employed. For thechecking operation, the programming system is adjusted to advance a testtape three blocks during each test-signal cycle and the three blocks onthe test tape program the same voltage ratio into each test channel.Thus the potentials applied to the taps of the master potentiometer 46are equal during each successive cycle of the test procedure. Thecontacts of three relays 87, 88 and 90 are connected to control thecircuit extending from each of the input channels. Relays 87 and 88 areinitially energized and apply the output voltages of channels 1 and 2 tothe amplifier 89. The relay 90 is then energized to compare the voltageon channel 1 with the voltage on channel 3. If the difference betweenthe adjacent tap voltages at any time exceeds a predetermined amount, astop relay 91 is energized to stop the feeding of the tape, whichindicates that the register and control system is out of adjustment ornot operating properly. The programming system is then serviced torepair or replace any defective element.

.Obviously the potentiometer 46 may *be provided with only two taps ormore than three taps, with a corresponding number of input channels.FIG. 7 illustrates the modification wherein two D/A converters 95 and 96are connected to the two taps of the resistance element 97 of the masterpotentiometer. The circuit is otherwise the same as shown and describedabove in FIGS. 1 to 4. In case more than three channels are employed, acorresponding number of equally spaced taps is provided on the masterpotentiometer.

It will be seen that the invention provides a programming method for awinding machine which is superior to the existing laborious andpainstaking programming method. It is easier to set up for theproduction of different resistance elements and the possibility of humanerror is eliminated. The apparatus used comprises standard electronicand mechanical devices which are readily available, interconnected in anovel manner in accordance with the invention.

What is claimed is:

1. An apparatus for winding a precision resistor for a potentiometer,comprising a servo-controlled winding machine having a servomotor drivemechanism, and means including a reference potentiometer for programmingthe winding of the resistance wire by said winding machine, saidreference potentiometer having a movable contact connected to saidservomotor drive mechanism and synchronized with the winding operationof said winding machine, said programming means further includingcontrol signal sensing and storage means for a multiplicity of controlsignals, connected to said reference p0: tentiomter for applyingvoltages corresponding to said control signals to the programmingfunction. 2. An apparatus according to claim 1, in which said referencepotentiometer has a plurality of taps along the resistance elementthereof, and switching means is provided to connect control voltagescorresponding to said stored control signals to said taps in timedrelation to the progressive winding operation.

3. An apparatus for winding a precision resistor for a potentiometer,comprising a servo-controlled winding machine, means for continuouslychecking the resistance Rx of the wound portion of the resistor as it isformed,

means including a reference potentiometer for programming said windingmachine, said programming means further including control signal sensingand storage means for a multiplicity of coded control signals, and

means for successively applying said control signals to said referencepotentiometer to control the programming function.

4. An apparatus according to claim 3, in which said means forcontinuously checking the resistance Rx of the wound portion of theresistor includes a constant-current source in series relation with saidwound portion, and the winding of the resistor is controlled by therelation between the potential drop across resistance Rx and a potentialderived from said reference potentiometer.

5. An apparatus for winding wire to form a precision resistor for apotentiometer, comprising a servo-controlled winding machine having aservomotor drive mechanism for an operating shaft of said windingmachine,

a reference potentiometer for programming the winding of the resistancewire by said winding machine to form a resistor having the desiredfunctional characteristics, said reference potentiometer having themovable contact thereof synchronized with the operating shaft of saidwinding machine,

means including the movable contact of said reference potentiometer forcontrolling said servomotor drive mechanism for the winding machine,

at least two taps on said reference potentiometer, and

means for applying control voltages to said taps on said potentiometerfor brief successive intervals in timed relation to the progressivewinding of the resistor being formed, to control the servomotor drivemechanism and thereby the spacing of the turns of wire on said resistor.

6. An apparatus according to claim 5, in which control signalsrepresenting said control voltages are stored in digital form insignal-storage means and a digital to analog converter is connectedbetween the signal-storage means and each tap on said referencepotentiometer.

7. An apparatus according to claim 6, in which said signal-storage meanscomprises a punched tape and a tape reader stepped concurrently with theadvance of the movable contact of the reference potentiometer from onetap to another.

8. Apparatus for winding a precision resistor for potentiometers, incombination,

a servo-controlled winding machine in which the functionalcharacteristics of the resistor being wound are controlled by varyingthe servo drive,

means for programming the operation of the servomotor, including alinear potentiometer having a plurality of equally spaced taps and aslider synchronized with the operation of the winding machine, saidprogramming means further comprising control signal-sensing and storagemeans for multiplicity of control signals, and

switching means for connecting control signals from said signal-sensingand storage means in predetermined sequence to the taps on said linearpotentiometer.

9. The method of controlling a winding machine for winding a resistorelement with a predetermined spatialresistance function, said windingmachine including a servomotor drive mechanism and a referencepotentiometer connected to said servomotor driving mechanism, comprisingthe steps of storing control signals representing the functionalcharacteristics of the resistor element to be wound on the windingmachine, and

applying corresponding signals successively to said referencepotentiometer during the winding operation to control the operation ofthe servomotor drive mechanism.

10. The method according to claim 9, which includes the steps of storingthe control signals on tape and stepping said tape in timed relation tothe progress of the winding operation.

11. The method of controlling a winding machine for winding a resistorwith a predetermined spatial-resistance function, said winding machineincluding a servomotor drive and programming means for controlling saidservomotor drive, comprising the steps of storing control signalsrepresenting the desired functional characteristics of the resistor, and

utilizing said control signals sequentially during the winding operationto control the servomotor drive.

12. In a servo-controlled winding machine for winding a resistor havinga predetermined spatial-resistance function, in which the programmingconsole includes a plurality of control-signal input channels andcorresponding voltage output circuits, the method of checking theoperativeness of the system which comprises the steps of operating theprogramming console through the steps of a normal cycle,

applying the same signal input to all said input channels during eachstep of the cycle, and

stopping the sequential operation of the system upon the occurrence of adiiference exceeding a predetermined amount between any two voltages inthe output circuits.

References Cited UNITED STATES PATENTS 2,964,252 12/ 1960 Rosenberg242-9 2,989,256 6/ 1961 Lee 242-9 3,128,956 4/ 1964 Schumann 242-93,166,104 1/1965 Foley et a1 242-9 XR 3,181,061 4/ 1965 Schneider 324-623,203,633 9/1965 Altieri 2424-9 3,237,657 3/ 1966 Elvers et al 242-9 XRBILLY S. TAYLOR, Primary Examiner.

US. Cl. X.R.

553 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3, 44 071 Dated May 20, 1969 Inventor(s) Charles F. Kezer and Thomas P.Zingarelli II It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 57, after "preferably" insert--c1amped-.

Column 6, lines 42 and 43, "potentiomter" should read--potentiometer--.

Column 7, line 31, "servo" should read--servomQt0r--' line 37, after"for" ins'ert--a--.

SIGNED AND SEALED (SEAL) Attest:

Edward M. Fletcher. Ir. I I R W ILL AM E- SCIHUYLER, J

Auestmg Officer Commissioner of Patents

